Driving licenses, valid and in force, issued by British authorities enable their holders to drive in our country until April 30, 2022.
As from 1 May 2022, licences issued by British authorities will enable drivers to drive in Spain for six months as from the arrival by the holder in Spain or from the date that legal residency is obtained.
More information:
https://www.dgt.es/comunicacion/noticias/dgt-brexit/ (Ministry of Home Affairs)
Non official translation